To add another anecdote to EricP's, my 4-yr state school charged the same based on everyone taking 15 hours. It was the same price form 12-18 hours, and they charged extra when you went over 18. I took in ~24 hours of AP credit, CLEP tested out of another 3, but still graduated on a 4 year plan. This was because of my particular engineering degree, which only offered certain courses in spring or fall and you had to complete them in sequence, and because not all the AP credit was applicable to my degree plan. It was impossible to graduate early unless you skipped through your entire freshman year; one friend of mine did do this, but they made an exception for him and he had to take some of those "freshman" courses later as a senior due to some silly rules. He's the only one that's ever done it in our major.
Everyone else I knew in engineering used the opportunity of AP credit to 1) reduce courseload, 2) avoid summer school, or 3) free up spots to take other interesting (or pre-med) classes/do research/etc, which would have sent them over 4 years. A friend who was an English major at our school graduated a full year early purely on accident after using her AP credit; just goes to show it really did depend on the degree. I knew I wanted to do engineering, but not at what uni, so the AP credit was just an added bonus - I didn't know how it would exactly affect my graduation plans. Kudos to OP's daughter if she's got it all planned out though!
AP credit was definitely beneficial for me, but not because i graduated early. IMO it helped me keep awesome grades and graduate on-time. About 15% of our class did not. Most were working on med school pre-reqs they couldn't squeeze into an already-packed degree plan or had switched majors.
I did, however, manage an excellent PSAT score which took care of most of my financial worries. My parents generously supplemented my scholarships by giving me 10% the value of scholarships earned in living money every semester, and I took out a job for fun money. Not going to lie - the fact that I'd be directly benefiting from earning scholarships encouraged me to pick the school I did (and avoid student debt) and seek out lesser-known scholarships, some of which were an easy target (one was literally just test scores and a 1-sheet application and it got me $5000....has since lost funding from the state).